I had the chance to chat on Jan. 12 with Francisco Diez-Gonzalez, professor of food safety at the University of Minnesota.

1:00 p.m. Tom Karst: You were recently quoted in a story about pathogens on organic produce and how that compares with conventionally grown fruits and vegetables. How are you involved with that issue?

1:01 p.m. Francisco Diez-Gonzalez: Part of my  research has been focused on trying to answer the question (about the presence of pathogens on organic compared with conventionally grown produce), and there are a number of people at work on this particular area in different parts of the world. Maybe not sufficient (research) to actually to come up with a good answer that reporters like to get - (to say) organic vegetables would be more or less safe than conventional.

Our first attempt was several years ago. We did a study that we went out to sample farmers’ fields and collected produce directly there and we brought it to the laboratory and tested it for salmonella, E. coli 157 and also indicator organisms such as total E. coli. Again, that’s one thing we are trying to address by using longitudinal studies on the farm. The short answer is that I don’t think there that were strong indications that organic vegetables had more susceptibility of being contaminated as compared to conventional.

The first paper we did see some trend, but once we extended the sampling and included more farms, The trend was there but was not significant. The fact was there not that many conventional farms that supplied produce such as leafy greens, which are the ones that are more susceptible to E. coli.  The other reason I am saying there doesn’t seem to be very strong evidence that pathogens are going to be more commonly present in organic vegetables because our study did not find E. coli 157 or salmonella; we only found a couple positive samples among 2,600. There re many other studies that have shown that pathogen prevalence in vegetables is relatively rare. With the exception of listeria, actually. Listeria has been getting the headlines (lately) because of the cantaloupe outbreak, but there are some surveys that have found listeria positives in about 5% of the samples. We didn’t test for listeria.

1:05 p.m. Karst: FDA is developing the produce safety rules as we speak. Do they have enough information to advise Good Agricultural Practices relative to various farming practices?

1:06 p.m. Diez-Gonzalez: Yes and no. The “yes” of what I’m saying is that if (the FDA) wants to prevent cases like the cantaloupe outbreak from happening, that would have been prevented with existing knowledge of Good Manufacturing Practices.
Because the conditions in the (Colorado) plant, as far as I’ve read in the reports, seemed to have violated basic Good Manufacturing Practices that have been accepted for decades. (The FDA’s role) partly could be just to make to sure that producers and  packing sheds comply with simple Good Manufacturing Practices.

On the other hand, I think we still, at the research level, recognize the fact we are trying to understand how the organisms, the pathogens, are capable of surviving (and) how they can get into the produce.  The other main question is what methods can be effectively used to control them, or kill them,  once they are in the produce. The main problem is that fresh vegetables and fruits are supposed to be eaten fresh, so we don’t have the resources of effective treatments like cooking, canning or pasteurization n because that would affect the produce. So the answer is yes and no. I think the producers in California are being very proactive in learning from the E. coli 157 outbreaks in spinach and lettuce and implementing their own trade group regulations internally with relative good results. I would say they are making progress  in terms of implementing additional solutions at the farm to help in preventing any more of those cases.

1:09 p.m. Karst: Specifically, as far as organic agriculture, do you think your research,  so far,  tells you that they need to do anything differently than what they are doing now?

1:10 p.m. Diez-Gonzalez: A; The one thing that I have said, that I have been advocating, is for the National Organic Program to review the recommendations for the use of raw manure. When those recommendations were enacted more than ten years ago, we didn’t know what we know now. Some of our research has (shown)  that the older  manure you use, the less likely you will to find contamination. My point is that there is plenty of research done by other research groups that supports the idea that the organic regulations we currently have - that you can use raw manure in organic agriculture as long as there is more than 120 days between the applications of the manure and harvest. That time, in my opinion, is not sufficient.

1:11 p.m. Karst: What time would be sufficient?

1:12 p.m. Diez-Gonzalez: That’s a good question, because (authorities) would have to look carefully to the scientific literature. The problem with this research  field is that some people have reported more than 200 days, some people have reported actually less than 120 days, some people have reported different numbers. That’s a big question, I would guess, who is going to make the decisions on what is an acceptable time that will minimize the risks that there will be viable pathogens by the time you will be harvesting vegetables. That’s a big question, and the other question is whether you are going to be applying raw manure and the produce is going to be contaminated and if the organisms are gong to survive on the produce. Surviving on the produce is also affected by the soil type, by the weather and also by the particular (pathogen ) strains. My recommendation is not to give you a specific number, but that the number needs to be reconsidered in light of what we have learned in the past 10 years. This should be done by a panel of experts that can review the literature and come up with their own expert opinion and come up with a new recommendation.